Break out RemoteBitrateEstimator from RtpRtcp module and make RemoteBitrateEstimator::Process trigger new REMB messages.

Also make sure RTT is computed independently of whether it's time to send RTCP messages or not.

BUG=1298

Review URL: https://webrtc-codereview.appspot.com/1060005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@3455 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/rtp_rtcp/source/rtcp_receiver_unittest.cc

@@ -172,9 +172,10 @@ class RtcpReceiverTest : public ::testing::Test {
         remote_bitrate_observer_(),
         remote_bitrate_estimator_(
             RemoteBitrateEstimator::Create(
-                &remote_bitrate_observer_,
                 over_use_detector_options_,
-                RemoteBitrateEstimator::kMultiStreamEstimation)) {
+                RemoteBitrateEstimator::kMultiStreamEstimation,
+                &remote_bitrate_observer_,
+                &system_clock_)) {
     test_transport_ = new TestTransport();
 
     RtpRtcp::Configuration configuration;